[gentoo-user] Linux too damn slow if memory > 3GB
Daniel van Ham Colchete
May be somebody can shed some light here... I'm building a server here with 4GB of RAM memory. The fact is, if I boot with mem=3072M everything goes as fast as it should but I'm not using 1GB of memory. If I don't put the mem option, Linux will see 4GB of memory available but it will be damn slow (really).
To make Linux recognize 4 gigs of memory I had to activate HIGHMEM=64GB, otherwise it only recognizes 3279MB (but it is fast).
My processor is a Intel Core 2 Duo E6320 (1.86Ghz). The motherboard is Intel. I'm running Gentoo at 32bits mode and the kernel version is 2.6.20-gentoo-r8.
Any lights would be very appreciated.
Best regards,
Daniel Colchete
Tim Allingham
I don't actually run 4GB of RAM in any of my intel systems, so I can't
comment from experience, however my suspicion would be the overhead
introduced from PAE, which (at least on older kernels) requires some
processing overhead to utilise. Are you able to try a 64-bit install to
determine if this is the case?
Regards,
Tim Allingham
Email:T...@DataFirst-IT.com.au
Tim Allingham
just to add, this page gives a reasonable explanation of the problems
with 32-bit OS's trying to address large RAM volumes
Daniel van Ham Colchete
The fact is I can't use 64bits for now... So let's take one gig out!
Thanks for your help!!!!
Daniel
Stroller
On 29 Jul 2007, at 00:28, Daniel van Ham Colchete wrote:
> ...
> The fact is, if I boot with mem=3072M everything goes as fast as it
> should but I'm not using 1GB of memory. If I don't put the mem
> option, Linux will see 4GB of memory available but it will be damn
> slow (really).
> My processor is a Intel Core 2 Duo E6320 (1.86Ghz). The motherboard
> is Intel. I'm running Gentoo at 32bits mode and the kernel version
> is 2.6.20-gentoo-r8.
Hi there,
Does your Intel motherboard feature the 945PM chipset?
I read about this last week:
http://listserver.themacintoshguy.com/pipermail/x4u/2007-July/
018031.html
Stroller.
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Daniel van Ham Colchete
actually it's the 965, but the link Tim sent me shows that it's not a chipset limitation... It's a 32bits design limitation...
Best,
Daniel
Developer Edoceo
Daniel van Ham Colchete skrev:
> actually it's the 965, but the link Tim sent me shows that it's not a
> chipset limitation... It's a 32bits design limitation...
Thats not true, I run 32bit Gentoo with 4 GB Memory and has no slowdown
issues I can measure with the naked eye.
Seems to me like you have some hardware problem.
I have two Gentoo systems (2.6.x) one with 4G and another with 8G. Both systems are are wicked fast. On the 4G `free` shows all but 21K of physical used, on the 8G there's still 2G free and the system is highly responsive. Can't remember which MB chipset I have, sorry. multiple Intel multicore cpu in both.
Daniel van Ham Colchete
What kernel version are you using?
Duane Griffin
> Hello everyone!!!
>
> May be somebody can shed some light here... I'm building a server here with
> 4GB of RAM memory. The fact is, if I boot with mem=3072M everything goes as
> fast as it should but I'm not using 1GB of memory. If I don't put the mem
> option, Linux will see 4GB of memory available but it will be damn slow
> (really).
It sounds like a problem with a buggy BIOS not setting up your MTRR
properly. This means linux ends up using ultra-slow memory for
important stuff. The problem has been discussed quite a bit on LKML,
see here, for example:
http://marc.info/?l=linux-kernel&m=118072237228294
> Any lights would be very appreciated.
Try upgrading to the latest BIOS version available for your
motherboard. If that doesn't fix it you will have to tell linux not to
use the affected memory. You can find out where that is by checking
your dmesg and /proc/mtrr, as described in the message referenced
above. Post the information here if you aren't sure.
Cheers,
Duane.
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